/*
 * Copyright (c) 2003, 2005, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
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 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package com.sun.jmx.remote.security;

import java.security.AccessControlContext;
import java.security.AccessController;
import java.security.CodeSource;
import java.security.Permissions;
import java.security.ProtectionDomain;
import javax.security.auth.Subject;
import javax.security.auth.SubjectDomainCombiner;

/**
 * <p>This class represents an extension to the {@link SubjectDomainCombiner}
 * and is used to add a new {@link ProtectionDomain}, comprised of a null
 * codesource/signers and an empty permission set, to the access control
 * context with which this combiner is combined.</p>
 *
 * <p>When the {@link #combine} method is called the {@link ProtectionDomain}
 * is augmented with the permissions granted to the set of principals present
 * in the supplied {@link Subject}.</p>
 */
public class JMXSubjectDomainCombiner extends SubjectDomainCombiner {

  public JMXSubjectDomainCombiner(Subject s) {
    super(s);
  }

  public ProtectionDomain[] combine(ProtectionDomain[] current,
      ProtectionDomain[] assigned) {
    // Add a new ProtectionDomain with the null codesource/signers, and
    // the empty permission set, to the end of the array containing the
    // 'current' protections domains, i.e. the ones that will be augmented
    // with the permissions granted to the set of principals present in
    // the supplied subject.
    //
    ProtectionDomain[] newCurrent;
    if (current == null || current.length == 0) {
      newCurrent = new ProtectionDomain[1];
      newCurrent[0] = pdNoPerms;
    } else {
      newCurrent = new ProtectionDomain[current.length + 1];
      for (int i = 0; i < current.length; i++) {
        newCurrent[i] = current[i];
      }
      newCurrent[current.length] = pdNoPerms;
    }
    return super.combine(newCurrent, assigned);
  }

  /**
   * A null CodeSource.
   */
  private static final CodeSource nullCodeSource =
      new CodeSource(null, (java.security.cert.Certificate[]) null);

  /**
   * A ProtectionDomain with a null CodeSource and an empty permission set.
   */
  private static final ProtectionDomain pdNoPerms =
      new ProtectionDomain(nullCodeSource, new Permissions());

  /**
   * Get the current AccessControlContext combined with the supplied subject.
   */
  public static AccessControlContext getContext(Subject subject) {
    return new AccessControlContext(AccessController.getContext(),
        new JMXSubjectDomainCombiner(subject));
  }

  /**
   * Get the AccessControlContext of the domain combiner created with
   * the supplied subject, i.e. an AccessControlContext with the domain
   * combiner created with the supplied subject and where the caller's
   * context has been removed.
   */
  public static AccessControlContext
  getDomainCombinerContext(Subject subject) {
    return new AccessControlContext(
        new AccessControlContext(new ProtectionDomain[0]),
        new JMXSubjectDomainCombiner(subject));
  }
}
